Insects and Parasitic Diseases. 57 



H. microstoma shown in Fig. 32, and with that stage of H. miiscae 

 ■designated bv Kansom, Stage No. 6. 



This final larval stage of H. megastoma found in the body of the 

 adult fly on one occasion only, has also been found frequently, in 

 "Company with adults, Avithin stomach tumours. Measurements and 

 ■details of a number of examples of this final stage are given in 

 •Table 4. 



Thus between the very early stages represented by embryos such 

 as that shown in Fig. 37, and very advanced stages such as shown 

 in Figs. 48 and 48A, both of which were recovered from the interior 

 •of tumours, there is a considerable number of stages of develop- 

 ment never yet found in the stomach tumours or in the digestive 

 -canal of the host, but which' form a continuous series of progressive 

 steps, almost entirely (Figs. 39-47) passed in the body of the 

 larva, pupa and imago of Musca domestica, the final stage (Figs. 

 48 and 48A), being found both in Musca domestica (adult), and in 

 the contents of the stomach tumours of the horse, where they 

 develop into the adult worm. 



Summapy and Discussion. 



It will be seen from an analysis of the experiments carried out 

 to determine the relationship of Musca domestica and Stomoxys 

 •calcitrans to the embryo of H. megastoma that Musca domestica 

 exclusively was used in four experiments, and that infection took 

 place in three of these experiments. The failure to infect flies in 

 the fourth experiment cannot be accounted for. 



In the positive experiments 35%, 52%, and 15% respectively of 

 the larvae, pupae and adults examined, were infected with from 

 one to sixteen parasites each. ' 



Stomoxys calcitrans exclusively was used in two experiments, in 

 both of Avhich there was no infection. 



It was intended to carry out further experiments, viz. : — (1) A 

 -culture of embryos of H. microstoma and H. megastoma fed to 

 larvae of both species, and (2) a culture of embryos of all three 

 species of Habronema fed to larvae of both species of fly. Time 

 however did not permit of this being done, nor, chiefly for this 

 same reason, was it found practicable to experiment with other 

 species of Musca. 



These experiments show that (1) Musca domestica is an inter- 

 mediary host of H. megastoma, and (2) all the available evidence is 

 against Stomoxys calcitrans acting, even accidentally, in such 



